Differential-microphone repeater.



1. 1. comm. DIFFERENTIAL MICROPHONE REPEATER.

APPLICATiON FILED FEB. I3, 1911- RENEWED SEPT. I2 I'IM 1 1 37, 18 8, l Patented Apr. 27,1915.

2 SHEETS-SHEET l- J. J. COMER.

' DIFFERENTIAL M'CROPHONE REPEATER. irrucmou men rm. 1s. ISM-RENEWED SEPT. 12. m4. 1 Patented Apr. 27, 19 I 2 SHEETS-SHEET 2.

' UNITED STATES PATENT OFFICE.

JOHN J. COMER, OF CHICAGO, ILLINOIS, ASSIGNOR- T0 AUTOMATIC ENUNCIATOR COMPANY, OF .GHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

DIFFERENTIAL-MICROPHONE REPEA'IER.

Specification of Letters Patent.

Patented Apr. 27, 1915.

Application filed February 13, 1911, Serial No. 608,386.. Renewed September 12, 1914. Serial No. 861,484.

To all whom it may concern Be it known that 1, JOHN J. CoMnR, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvement in Differential-Microphone Repeaters, of which the following is a specification.

My invention relates to microphone transmitters in general, but more particularly to microphones of the so -called differential type, and especially to differential microphone repeaters for use in loud speaking or other telephone systems. I

Generally stated, the object of my invention is to provide an improved and highly eflicient differential microphone for use in telephone transmitters, or, for use in telephone repeaters, in which the arrangement of the electrodesis simple and effective, and in which the operative connection or stem does not, even when the microphone is used in a repeater, pass through both walls thereof, but only through one, whereby the construction is simplified and the method of applying and regulating the spring tension necessary to the operation of a repeater is rendered more satisfactory than heretofore, as will hereinafter more fully appear.

To the foregoing and other useful ends,

' my invention consists in matters hereinafter set'forth and claimed.

In the accompanying drawingsFigure 1 is a view of one side of a differential microphone repeater.with the casing thereof removed to show the construction. Flg. 2 is a similar view of another 'side of said repeater. Fig. 3 is a front elevation of. the repeater shown in Figs.- 1 and 2. Fig. 4 1s a transverse section through the microphone portion of said repeater on line 44 in Fig. 2. Fig. 5 is a similar section on line 5'-5 in Fig. 2. Fig. 6 is an. enlarged longitudinal section of the forward or microphone end of the repeater shown in Figs. 1 and 2. Fig. 7 is a collective view of the different parts of the microphone box, showing the said parts separated, and some of said parts being in section.

A thus illustrated, and referring more particularly to Figs. 1,2 and 6, it will be seen that my invention comprises a permanent magnet A'of any suitable, known or approved construction. The pole piece a is clamped between the shorter limb a of p the said magnet and the block a which latter rests upon the inner side of the longer limb a of said magnet. A bracket a which engages the limb a, and a bracket 0. which engages the limb a are clamped to the magnet by the screw a, which latter also passes through the block a and the pole piece a,

whereby the structure is drawn tightly together. The pole piece a has a coil or winding a it being observed that the limb a and the pole piece a are about flush at their outer ends. The limb 0, has its end provided with a shoulder a which serves as a support for the lower edge of the armature (19, which latter is held in place on said shoulder by the magnetism of the permanent magnet, the said armaturp being of such length that .its upper end is opposite the pole piece a,

and is adapted to be attracted by the latter when the coil or winding is energized by telephonic currents.

The differential microphone box Bis suit-' ably securedto the outer ends of thebrackets a and a The said box comprises a ringlike back plate -b of suitable metal, a front plate I) of suitable metal, which plates are connected together by bolts b and suitably spaced apart by sleeves b of suitable insulating material, which sleeves inclose said bolts. The central opening I) in the back plate 6 is closed by a disk-like sheet of insulation 6 and a similar sheet of insulation 6 bears against the inner surface of the plate 6, in the manner shown. A disk-like sheet of metal I) bears against the insulation 6, and a similar sheet of metal I) bears. against the insulation b; A carbon plate or diaphragm b is held against the metal terminal plate I), and a carbon plate 6 is held against the metal terminal plate 6", these two carbon plates serving as stationary electrodes for the microphone. A ring of insulation b fits against the inner surface of the carbon plate b,, and a of insulation b rests against the flat surface of the carbon plate or electrode 6, these two rings being spaced apart by collars I) that encircle the sleeve b. The space between these two rings 12 and b is-filled with fibrous asbestos b, or other suitable material, whereby a chamber is formed at the center of the box for holding the granular carbon 6 or other suitable material. Thelplunger-like or movable electrode b" is embedded in the center of the mass of granduring its condition while active or in operation. The said spring is adjustably connected to the threaded stem 6 which has an eye 6 at its outei end. The electrode 6 may be of carbon, or other suitable materlal,

and when vibrated serves to alternately vary the distance at each side thereof, itbeing understood that the circuits of said electrodes may be of any suitable, known or approved character, such, for example, as those commonly employed for differential microphone transmitters.

The lever orarm C is pivotally mounted in a recess 0 formed in the bracket a, as by a screw 0', and its outer and upper end is controlled by an adjusting screw 0 that has threaded engagement with .an opening in the bracket a there being a spring 0? interposed between said arm and bracket, wherebyrotation of the screw will move the arm one way or the other. At its lower pivoted end the said arm or lever carries a vertical screw 0', and the lower end of this screw carries a tubular portion 0 that has a slight internal flange at the lower end thereof, which flange has a knife edge and is adapted to support the headed upper end of the lever 0 This lever, it will be seen, extends downward to the eye 6 0f the stem of the movable electrode. A link a" connects the said lever with the projection 0 on the upper end of the armature, the said lever passing through the link, whereby the lever can be moved up and down in the link to change the point of connection therewith, by rotating the screw 0. This, of course, will vary the distance between the'link and the fulcrum of said lever, which fulcrum is atthe point Where the lever is supported by "the hollow or tubular .fulcrum c on the lower end of the screw c and will vary the leverage. The position of the armature a, relative to the pole piece a, and the tension of the spring b, are regulated by the screw 0 as adjustment of this screw will move the fulcrum of the lever 0 either. toward or away from the microphone box, thus accomplishing the desired adjustment for regulation.

Thus it will be seen that I provide an improved differential. microphone repeater. in whichthe stem of the movable electrode extends through only one side of the box, and

- air gap between the arinature and its in which the latter is of simple and effective construction, and of such character that heavy currents can be carried without dan- The P piece can be accurately regulated by the adjustment ofthe screw 0 and the screw 0 can be adjusted to vary the leverage of the lever c in accordance with the stiffness of the spring I), it being understood that the first or approximate adjustment of these different parts is obtained by properly adjusting the electrode 6 and the spring 6 on the stem b", at the time that they are secured thereon by ,nuts or other suitable devices. The said microphone box can be easily taken apart for the purpose of repair or substitution. I granular carbon after it is fully assembled, and said carbon will then be held in place by the insertion of the asbestos in the space between'the two rings 6 and 6 in the manner previously described. The spring 6, is, moreover, disposed between the microphone and the magnet mechanism, and is easily removed and put in place. The insulating parts of the microphone box can be of any suitable character, such as mica ger of over heating or other trouble.

or fiber or rubber'vulcanite, or any other suitable insulating material that can stand considerable heat if it becomes necessary to employ heavy currents.

With the construction shown, it will be observed that the granular carbon at one, side of the movable electrode is separated from the granular carbon at the other side thereof. This is by reason of the engagement of the fibrous material 6 with the circumference or edges of the said electrode. This engagement does not interfere with the free and proper vibration of the said electrode, and the results, I find, with this construction, are entirely satisfactory.

What I claim as my invention is:

1. In a differential microphone repeater, a microphone box provided with a movable stem for the operation thereof, a magnet provided with an armature, a connection between the armature and said stem, and a spring opposing the action of said armature, applied to said stem at a point between the armature and box. 2. In a differential microphone repeater, a microphone box provided with a movable stem for the operation thereof, a magnet provided with an armature, a connection between the armature and said stem, a spring opposing the action of said armature, applied to said stem at a point between the armature and box, and means for regulating the tension of said spring. In a difierential microphone repeater,

a microphone box provided with a movable stem for the operation thereof, a magnet provided wlth an armatufie; a connection be- It can-be filled with the tween the armature and said stem, a spring opposing the action of said armature, applied to said stem at a point between the armature and box, said spring consisting of 5 a flat strip of spring-metal mounted transversely on the said stem, and means for engaging the ends of said spring. 1

4. In a differential microphone repeater, a microphone box provided with a movable stem for the operation thereof, a magnet provided with an armature,-a connection between the armature and said stem, and a spring opposing the action of said armature, applied to said stem at a point between the armature and box, the said connection between the stem and armature comprising a lever.

5. In a differential microphone repeater, a microphone box provided with a movable stem for the operation thereof, a magnet provided with an armature, a connection between the armature and said stem, and a spring opposing the action of said armature, applied to said stem at a point between the armature and'box, the said connection between the armature and the stem consisting of a variable leverage connection.

.6. In a differential microphone repeater, a microphone .box provided with a movable stem for the operation thereof, a magnet provided with an armature, a connection between the armature and said stem, and a spring opposing the action of said armature, applied to said stem at a point between the armature and box, there being a lever in the connection between *the stem and armature, a fulcrum for said lever, and means for shifting said fulcrum to regulate theair gap of said armature and the tension of said spring.

7. In a differential microphonerepeater, a microphone box provided with a-movable stem for the' operation thereof, a magnet provided with an armature, a connection between the armature and said stem, and a spring opposing the action of said armature, applied to said stem at a point between the armature and box, the said microphone box having a back plate with a central opening therein, which opening is provided with a flange for engaging the ends of said spring.

j 8. In a differential microphone repeater,

a microphone box provided with a movable stem for the operation thereof, a magnet provided with an armature, a connection between the armature and said stem, and a spring opposing the action of said armature, applied to said stem at a point between the armature and box, said microphone box being closed circumferentially by a filling of fibrous material, and having a movable or plunger-like electrode, the circumferenceof which is engaged by the inneredges of said filling of fibrous material.

box and a diaphragm, an electromagnet and an armature therefor, a lever extending substantially parallel to said diaphragm, a

fulcrum for one end of said lever, means for adjusting said fulcrum for regulating the leverage, a connection from said lever to said diaphragm, a stem connected to said lever and said armature, and a second connection from said lever to said armature, and a spring opposing the action of said armature applied to said stem at a point between the armature and said diaphragm.

11. In a telephone amplifier, a microphone transmitter comprising a variable resistance box, a diaphragm and a movable stem secured to said diaphragm, an electromagnet and an armature therefor, a lever pivoted at one end, a link connection at an intermediate polnt of said lever to said. armature, and

a connection from the opposite end to said stem, and a spring opposing the action of sald armature applied to said stem at a point between the armature and the box.

12. In a telephone amplifier, a microphone transmitter comprising a resistance box and a diaphragm, an electromagnet and an armature therefor, a lever extending substantially parallel to said diaphragm, a fulcrurn for one end of said lever, means for adjusting said ful'crum for regulating the leverage, a link connection from said lever to said diaphragm, a stem connected to said lever and said armature, a second connection from said lever toisaid armature, and a spring opposing the action of said armature applied to said stem at a point between the armature and said diaphragm.

13. In a telephone amplifier, a microphone transmitter, a movable central electrode therefor, a lever, a connection from said electrode to the lever, a fulcrum for said lever, a pivoted support onwhich said fulcrum isadjustably mounted, an electromagnet, an armature therefor, a connection from said armature to said lever, and means for adjusting said support about its axis, the 'adjustment of the fulcrum on said support serving to vary the leverage, and the adjustment of he said support serving to vary the air gap between said magnet and armature.

14. In a telephone amplifier, a microphone transmitter, a movable central electrode therefor, a lever, a connection from the lever to said member, a fulcrum for said lever, a pivoted support on which said fulcrum is adjustably mounted, an electromagnet, an armature therefor, a connection from said armature to said lever, and means for adjusting said support about its axis, the adjustment of the fulcrum on said support serving to vary the leverage, and the adjustment of the said support serving. to vary the air gap between said magnet and armature.

I 15. In a telephone amplifier, a microphone transmitter, a movable central electrode therefor, an electromagnet, an armature therefor, a lever, a link connection from the electrode to the lever, said connection being secured to said electrode, a connection from the lever to the armature, a fulcrum for said lever, and means for adjusting said fulcrum to regulate the air gap between said magnet and armature.

16. In a telephone amplifier, a microphone transmitter, a movable central electrode therefor, a lever connected to said electrode, an electromagnet provided with an armature for operating said lever, means for changing the leverage, and pivoted means for mechanically regulating the tension of said electrode and the air gap between said magnet and armature.

17 In a telephone amplifier, a microphone transmitter, a movable central electrode therefor, a lever connected to said electrode, an electromagnet provided with an armature for operating said lever against the tension of said electrode, a screw for moving said lever longitudinally for changing v the leverage, and a screw for mechanically regulating the tension of said electrode and the air gap between said magnet and'armature.

18. In a telephone amplifier, a microphone transmitter, a movable central electrode therefor, an electromagnet, an armature therefor, a lever pivoted at one end, a link connection from the opposite end of said lever to said electrode, and a link connection at an intermediate point of said lever to said armature.

19. In a telephone amplifier, a microphone transmitter, a movable central electrode therefor, a polarized electromagnet, an armature therefor, a lever pivoted at one end, a link connection from the opposite end of said lever to said electrode, and a link connection at an intermediate point of said lever to said armature.

20. In a telephone amplifier, a microphone transmitter, a movable central electrode therefor, an electromagnet, an armature therefor, a lever extending substantially parallel to said electrode, a fulcrum for one end of said lever, and means for adjusting said fulcrum for regulating the leverage, a

connection from said lever to said electrode,

and a second link connection extending from said lever to said armature.

1 21. In a telephone amplifier, a microphone therefor, an electromagnet, an armature therefor, a lever extending substantially- JOHN J. OOMER.

Witnesses LnwIs, RUSSELL KEARNS.

transmitter, a movable central electrode- 

